Penicillium Viridicatum Research Articles

Agro-waste as a substrate for the production of pullulanase by Penicillium viridicatum under solid-state fermentation

One of the key enzymes utilized in the food industry is pullulanase. But its major drawbacks are its low yield and high production costs. In this regard, the current research aims to screen agro-waste substrates for optimal pullulanase production in solid-state fermentation. Of various agro-wastes used as a substrate, the maximum enzymic activity (9.74 U/gds) was observed in a medium based on 5 g of green gram husk and incubated for 3 days at 30 °C. The effects of 16 different nutrients on the yield of pullulanase production were studied using the Plackett–Burman experimental design. The incorporation of FeSO4, MnSO4, and MgSO4 into the pullulanase production medium significantly increased the yield and showed a 5.7-fold increase (56.25 U/gds) in comparison with the unoptimized media. The Box-Behnken experimental design was used to study the effect of interactions between Fe2+, Mg2+, and Mn2+ on the production of pullulanase. Box-Behnken showed a 1.1-fold increase (62.1 U/gds) in pullulanase production. The total increase in yield after all optimization was 6.37-fold. The present study reports for the first time the applicability of green gram husk as a potent substrate for pullulanase production by Penicillium viridicatum.

Antimicrobial and Antiochratoxic Activities ofMentha spicataEssential Oil

The principle aim of this work is to evaluate the antimicrobial and antiochratoxic power of the essential oil ofMentha spicata(EOM). This oil was obtained by hydrodistillation with a yield of 0.3%. EOM was screened for its possible antibacterial activity in vitro against five strains of pathogenic bacteria, using the solid disc diffusion method and the microdilution method. The extract reacted positively to the bacterial strains tested. The results of the antifungal activity show an inhibition of mycelial growth; it is total onAspergillus ochraceus,Aspergillus flavus,Aspergillus niger,Penicillium viridicatum, and onRhizopus stoloniferandAlternaria alternateat a concentration of 12.5 μl/ml. Tests carried out on yeasts mainly referenced asCandida albicansIP444 andCandida albicans2679 showed minimal inhibition (MIC) of the order of 7.81 μl/ml and 0.97 μl/ml, respectively and theMICis of the order of 0.48 μl/ml forCandida albicans10 231. In addition, the EOM antiochratoxigenic test for ochratoxin A production capacity following a series of high performance liquid chromatography separation and ultraviolet detection (HPLC–UV) analyses detected an inhibitory effect proportional to the EOM concentration. In general, the essential oil showed an effective antimicrobial action on the growth of the tested pathogens and an antiochratoxigenic.

Preparation and characterization of k-carrageenan/konjac glucomannan/TiO2 nanocomposite film with efficient anti-fungal activity and its application in strawberry preservation

A nano-composite film was prepared from k-carrageenan (KC), konjac glucomannan (KGM) and TiO2 nanoparticles (NPs) by solvent casting method. The morphology and structure of the KC/KGM based nano-composite films prepared from different weight ratio of TiO2 NPs were characterized by SEM, XRD and FT-IR techniques. The addition of TiO2 NPs to KC/KGM films improved the mechanical, thermal, structural, and barrier properties of nano-composite films. In particular, the film containing 7 wt% of TiO2 NPs exhibited effective photocatalytic anti-fungal activity (79%) for Penicillium viridicatum after irradiating 6 h through generating reactive oxygen species thus destroying the fungi. Benefitting from the improved characteristics investigated above, the nano-composite films showed a favorable effect on strawberry storage. Overall, the fabricated KC/KGM/TiO2 nano-composite films have a broad application in the field of food preservation and packaging applications.

Antifungal activity of endophytic fungi from Cupressaceae against human pathogenic Aspergillus fumigatus and Aspergillus niger

Aspergillus is a fungal genus that strongly affects health of humans, animals, and plants worldwide. Endophytes are now widely considered as a rich source of bioproducts with potential uses in medicine, agriculture, and bioindustry. Cupressaceae plant family hosts a variety of bioactive ascomycetous endophytes. In this study, antifungal activity of a number of such endophytes were investigated against human pathogenic fungi Aspergillus fumigatus and Aspergillus niger. To this end, 16 superior bioactive endophytic fungi from Cupressaceae were used, including Alternaria alternata, Alternaria pellucida, Ascorhizoctonia sp., Aspergillus fumigatus, Aspergillus niger, Aurobasidium sp., Cladosporium porophorum, Fusarium oxysporum, Penicillium viridicatum, Phoma herbarum, Phoma sp., Pyrenochaeta sp., Trichoderma atroviride, Trichoderma atroviride and Trichoderma koningii. In vitro bioassays indicated anti-Asperilli activity of the endophytic fungi in dual cultures. Most notably, Trichoderma koningii CSE32 and Trichoderma atroviride JCE33 showed complete growth inhibition of both A. niger and A. fumigatus, within 3 to 7 days. Also, volatile compouds (VOCs) of T. koningii CSE32 and T. atroviride JCE33 exhibited 33–100% growth inhibition of A. niger, whithin 3 days. Moreover, on the day 7, growth of A. niger was less affected than that of A. fumigatus. In general, it appears that there is a direct relationship between the exposure time and the inhibitory activity of endophytes VOCs on the growth of target Aspergillus species. Furthremore, the extracellular secondary metabolites (SMs) of four selected fungal endophytes exhibited anti-Aspergillus activity at all treatment levels as shown by Agar-diffusion assay. SMs from T. koningii CSE32 and Pyrenochaeta CSE134 showed strongest activities against A. niger, and SMs from T. koningii CSE32 and F. oxysporum CAE14 showed strongest activities against A. fumigatus. In conclusion, given the globally recognized issue of antibiotic resistance and the urge to discover new antimicrobial substances, our findings provide new insights into the potential use of Cupressaceae's endophytic fungi in antifungal-based drug discovery programs.

Antifungal Activity of Crude and Phenolic Extract to Rice Crusts and Chemical Pesticide (Blitinute) in Inhibition of Fungi Isolate from Rice Seeds

Objective: The major goal regarding the presented study is to evaluate the impact of the Rice extract from Rice Crusts and chemical pesticide (Blitinute) on the growth of pathogenic fungi. Method: Rice seed samples were collected directly from farmers field for isolating significant pathogenic fungi related to the seeds. Anti-fungal activity assay of the crude, Phenolic extract and chemical pesticide were determined by agar plating-method against some pathogenic fungi. Result: obtained results showed the effect concentration of rice seed extract on growth of fungi especially phenolic extract had wide spectrum antifungal activity than crude extract. when the use of chemical pesticide (Blitinute) at a concentration of 0.3% with reaching rate of inhibition to 100% to Fusarium graminerum , Penicillium viridicatum, while (88.8) the same concentration for the Aspergillus fumigates. In another than the use Integrations between two extract and chemical pesticide (Blitinute) to high effect against test fungi than one extract and chemical pesticide. Conclusion: This study demonstrates that the presence of three pathogenic fungi (Aspergillus fumigatus , Fusarium graminerium, Penicillium viridicatum) related to the rice grains have been controlled at various concentrations of two extract (crude & phenolic) and chemical pesticide totally inhibited radial growth regarding all test fungi .

Herbicidal Polyketides and Diketopiperazine Derivatives from Penicillium viridicatum.

Herbicidal activity-guided isolation from the fermentation extract of Penicillium viridicatum had obtained two herbicidal series of polyketides (1-7) and diketopiperazine derivatives (8-11), especially including three novel polyketides (1-3). The structures and absolute configurations of new polyketides 1-3 were elucidated by extensive spectroscopic analyses, as well as comparisons between measured and calculated ECD spectra. Novel polyketides 1-3 and known 4, all bearing the heptaketide skeleton with a trans-fused decalin ring of 8-CH3 substitution, could significantly inhibit the radicle growth of Echinochloa crusgalli seedlings with a dose-dependent relationship. Especially at the concentration of 10 μg/mL, 1-4 exhibited the inhibition rates with 81.5% ± 2.0, 76.4% ± 0.8, 79.6% ± 1.1, and 80.0 ± 1.8%, respectively, even better than the commonly used synthetic herbicide of acetochlor with 76.1 ± 1.4%. Further greenhouse bioassay revealed that 4 showed pre-emergence herbicidal activity against E. crusgalli with the fresh-weight inhibition rate of 74.1% at a dosage of 400 g ai/ha, also better than acetochlor, while the other isolated metabolites (5-11) exhibited moderate herbicidal activities. The structure-activity differences of isolated polyketides indicated that the heptaketide skeleton, characterized by a trans-fused decalin ring with 8-CH3 substitution, should be the key factor of their herbicidal activities, which could give new insights for the bioherbicide developments.

Antifungal evaluation of plant essential oils and their major components against toxigenic fungi

Contamination of toxigenic fungi in foods, agricultural commodities and Chinese herbal medicines has posed serious threaten to human and animals’ health and safety. Natural antifungal agents from plant essential oils (PEOs) and their active components have been candidates of interest. In this study, the antifungal activities of PEOs from 11 natural plants against three kinds of toxigenic fungi including Aspergillus flavus, Penicillium viridicatum and Aspergillus carbonarius were evaluated and compared through the determination of fungi zone diameter. Results showed that 4 PEOs of Cinnamomum cassia Presl, Litsea cubeba, Cymbopogon martini and Thymus mongolicus Ronn expressed stronger inhibitory effects and lower minimal inhibitory concentrations (MICs) against the three kinds of fungi, which would be the ideal antifungal candidates. Then, the chemical compositions of them were analyzed by an optimized gas chromatography-mass spectrometry method with trans-cinnamaldehyde and d-limonene, citral and citronellal, trans-geraniol, and carvacrol as their main active components, respectively. The six compounds with strong antifungal activity and small MICs on the three kinds of fungi might contribute largely to the inhibitory effects of the 4 selected PEOs containing them. The 4 selected PEOs and their 6 main active components exhibited wide application prospect as the novel natural antifungal alternatives for preventing fungal contamination in different matrices to assure their quality and safety. The use of PEOs with highly-volatile components is environment-friendly, convenient and highly-effective with minimal residues and low cost will get more interest in practice.

Role of ethylene signalling in growth and systemic resistance induction by the plant growth‐promoting fungus Penicillium viridicatum in Arabidopsis

AbstractThe plant growth‐promoting fungi (PGPF) have long been known to improve plant growth and suppress plant diseases. The PGPF Penicillium viridicatum GP15‐1 elicited plant growth and induced systemic resistance (ISR) in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 (Pst), leading to a restriction of pathogen growth and disease development. Examination of local and systemic genes indicated that GP15‐1 did not modulate the expression of any of the tested defence‐related marker genes involved in salicylic acid (SA), jasmonic acid (JA) and ethylene signalling pathways. Subsequent challenge of GP15‐1‐colonized plants with Pst bacterium primed Arabidopsis plants for enhanced activation of the JA‐inducible Atvsp (vegetative storage protein) gene at a later stage of infection. To assess the contribution of different signalling pathways in GP15‐1‐elicited plant growth and ISR, Arabidopsis genotypes implicated in SA signalling expressing the nahG transgene (NahG) or carrying disruption in NPR1 (npr1), JA signalling (jar1) and ethylene signalling (ein2) were tested. The GP15‐1‐induced plant growth and ISR were fully compromised in an ein2 mutation. Root colonization assay revealed that the inability of the ein2 mutant to express GP15‐1‐induced plant growth and ISR was not associated with reduced root colonization by GP15‐1. In conclusion, our results demonstrate the ethylene signalling pathway is involved in plant growth promotion and ISR elicitation by the PGPF P. viridicatum GP15‐1 in Arabidopsis. These results provide evidence that ethylene signalling has a substantial role in plant growth and disease resistance.

Ochratoxin A levels in plasma from inhabitants of northern Paraná, Brazil

Ochratoxin A (OTA), a mycotoxin produced by some fungi likeAspergillus ochraceus, Aspergillus niger, Aspergillus carbonarius andPenicillium viridicatum, is a natural contaminant of many foods worldwide. The intake of OTA is associated with deleterious effects to humans and animals, such as nephro- and hepatotoxicity. Although there are some data about food contamination, there is lack of data about human exposure to OTA in Brazil. Therefore, current research aimed to determine the level of human exposure to OTA and, additionally, identify possible associations with biomarkers of liver and kidney damage. OTA levels were evaluated in plasma samples from 149 individuals living in the state of Paraná, Brazil, by indirect competitive ELISA using monoclonal antibody anti-OTA (cell line OTA.7). Plasma levels of OTA, alanine aminotransferase, aspartate aminotransferase, urea and creatinine were submitted to Pearson's correlation test. It was possible to measure OTA levels in 54.4% of the samples (mean 734±296 pg/ml; maximum 1,585 pg/ml), with an estimated daily intake of 983-1,445 pg/kg body weight. There was no correlation between OTA plasma levels and biochemical parameters, possibly due to the low level of contamination. This is one of the first studies concerning the contamination of humans by OTA in Brazil and we conclude that the plasma levels of the evaluated population indicate an estimated weekly intake below the tolerable weekly intake derived by the EFSA Panel on Contaminants in the Food Chain. Nevertheless, additional longitudinal studies with greater regional coverage and at different seasonal periods are necessary.

Material Properties and Antimicrobial Activity of Polyhydroxybutyrate (PHB) Films Incorporated with Vanillin.

Polyhydroxybutyrate (PHB) was produced by Bacillus mycoides DFC 1, isolated from garden soil. Antimicrobial (AM) films of PHB were prepared by incorporating vanillin (4-hydroxy-3-methoxybenzaldehyde) from 10 to 200 μg/g of PHB. The films were assessed for antimicrobial activity against foodborne pathogens and spoilage bacteria comprising of Escherichia coli, Salmonella typhimurium, Shigella flexneri, and Staphylococcus aureus and fungi such as Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus parasiticus, Aspergillus ochraceus, Penicillium viridicatum, and Penicillium clavigerum. The minimum concentration of vanillin required to exhibit antimicrobial activity was ≥80 μg/g PHB for bacteria and ≥50 μg/g PHB for fungi. The PHB films with and without vanillin were studied for mechanical and thermal properties such as tensile strength, Young's modulus, percentage elongation to break, melting temperature, and heat of fusion. The thermal stability of the films was studied using thermogravimetric analysis. The release kinetics of vanillin into food matrices was also checked using food stimulants. The study is intended to find applications for PHB films containing vanillin to enhance the shelf life of foods in the form of biodegradable wrapper.

The anti-giardial effectiveness of fungal and commercial chitosan against Giardia intestinalis cysts in vitro.

Chitosan with poly-N-acetylglucosamine sequences is a deacetylated derivative of chitin that can be found in the exoskeletons of crabs, shrimp and lobsters, the cuticles of insects and the cell walls of fungi. The aim of the present study was to compare the effects of fungal chitosan (FC) prepared from the cell walls of Penicillium viridicatum and Penicillium aurantiogriseum with commercially available chitosan (CC) against Giardia intestinalis cysts in vitro. The giardia cysts were isolated using a sucrose method. Four concentrations (50, 100, 200 and 400μg/ml) of each type of prepared chitosan were applied for 10, 30, 60 and 180min. The viability of the cysts was checked via 0.1% eosin staining. Our results indicate that P. viridicatum (with a 47.5% DD) and P. aurantiogriseum (with a 47.3% DD) at different concentrations after 180min precipitated, respectively, 56, 69, 81 and 100%, and 63, 75, 86 and 100% mortality rates. CC (with a 54% DD) showed 79, 84, 93 and 100% mortality rates. In conclusion, both FC and CC at 400μg/ml concentrations after 180min of exposure showed the most potent effect against G. intestinalis cysts. Accordingly, chitosan could be suggested as a new natural nanoform agent for future research in the safe and effective treatment of Giardia infections.

The Plant Growth-promoting Fungus Penicillium spp. GP15-1 Enhances Growth and Confers Protection against Damping-off and Anthracnose in the Cucumber

Plant growth-promoting fungi (PGPF) have the potential to confer several benefits to plants in terms of growth and protection against pests and pathogens. In the present study, we tested whether a PGPF isolate, Penicillium spp. GP15-1 (derived from zoysiagrass rhizospheres), stimulates growth and disease resistance in the cucumber plant. The use of the barley grain inoculum GP15-1 significantly enhanced root and shoot growth and biomass of cucumber plants. A root colonization study revealed that GP15-1 was a very rapid and efficient root colonizer and was isolated in significantly higher frequencies from the upper root parts than from the middle and lower root parts during the first 14 d of seedling growth. Inoculating the cucumber seedlings with GP15-1 significantly reduced the damping-off disease caused by Rhizoctonia solani, and the disease suppression effects of GP15-1 were considerably influenced by the inoculum potential of both GP15-1 and the pathogen. Treatment with the barley grain inoculum or a cell-free filtrate of GP15-1 increased systemic resistance against leaf infection by the anthracnose pathogen Colletotrichum orbiculare, resulting in a significant decrease in lesion number and size. Molecular and phylogenetic analyses of internal transcribed spacer sequences of the genomic DNA of GP15-1 revealed that the fungal isolate is a strain of either Penicillium neoechinulatum or Penicillium viridicatum.

In vitro treatments of Echinococcus granulosus with fungal chitosan, as a novel biomolecule

ObjectiveTo determined the antiparasitic activity of the isolated chitosan from Penicillium viridicatum, Penicillium aurantiogriseum and commercial chitosan against protoscolicidal of hydatid cysts were determined. MethodsAfter isolating chitosan from fungal cell walls, four concentrations (50, 100, 200, 400 μg/mL) of each type of prepared chitosan and commercial chitosan were used for 10, 30, 60, and 180 min, respectively. ResultsAmong different type of chitosan, commercial chitosan with the highest degree of deacetylation showed high scolicidal activity in vitro. Fungal chitosan could be recommended, as good as commercial chitosan, for hydatic cysts control. ConclusionsIt seems to be a good alternative to synthetic and chemical scolicidal.

Penicillium viridicatum RFC3, a new high β-glycosidase activity producer: a supplement of cellulases from Trichoderma reesei QM9414 for biomass saccharification

Penicillium viridicatum RFC3, a new high β-glycosidase activity producer: a supplement of cellulases from Trichoderma reesei QM9414 for biomass saccharification

Microbiological Safety of Ready-to-eat Foods Sold in Primary Schools in Abeokuta, South-West Nigeria

A study was conducted to assess the microbial safety of ready-to-eat (RTE) foods sold in private and public primary schools in Abeokuta, South-western Nigeria. One hundred and sixty RTE food samples were collected from forty food vendors in thirty primary schools and analysed microbiologically. Socio-economic status and their knowledge of food safety were assessed using the structured questionnaires. Total bacterial counts, total coliform counts and total fungal counts of RTE foods in public primary schools ranged from 6.27 log10cfu/g to 6.47 log10cfu/g, 6.00 log10cfu/g to 6.28 log10cfu/g and 5.85 log10cfu/g to 6.16 log10cfu/g respectively while those of private primary schools ranged from 6.30 log10cfu/g to 7.47 log10cfu/g, 6.15 log10cfu/g to 6.54 log10cfu/g and 5.60 log10cfu/g to 6.70 log10cfu/g respectively. Bacteria isolated from these samples were Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, Proteus spp, Enterobacter aerogenes, Shigella dysenteriae and Escherichia coli while the fungal isolates includeAspergillus niger, Aspergillus fumigatus, Rhizopus spp, Penicillium viridicatum, Mucor spp and Fusarium spp. RTE foods sold in both private and public primary schools were found to be highly contaminated. Inappropriate storage conditions, inadequate knowledge of food safety, attitudes and practices of the food vendors are the factors that may allow the food contamination. These findings demonstrate that ready-to-eat foods vended in public and private primary schools in Abeokuta, South-western Nigeria constitute an hazard to the pupils’ health. Provision of health education to the vendors and enforcing implementation of appropriate hygienic practices would improve food quality.Keywords · Ready-to-eat foods · Microbial safety · Primary schools

Investigating Two Native Algal Species to Determine Antibiotic Susceptibility Against some Pathogens

The aim of present study was to investigate antimicrobial activity of two algal species <em>Pithophora oedogonium</em> and <em>Botrydiopsis arhiza</em> against four bacterial species: <em>Salmonella</em> 1 (egg), Salmonella 4 (meat 2), <em>Staphylococcus</em> sp., 4978 and <em>Staphylococcus</em> sp., 5034 and four fungal species viz: <em>Aspergillus niger</em> 419, <em>Aspergillus flavus</em> 1110, <em>Penicillium viridicatum</em> 1101 and <em>Fusarium solini</em> 1127. The algal cell mass was extracted in 100% ethanol and further concentrations of 2, 4, 6 and 8 mg/mL were made. Antagonistic effects were tested by using disc-diffusion method for bacterial species and agar well technique for fungal species. <em>B. arhiza</em> did not exhibit antimicrobial activity against all the test organisms. Whereas the ethanol extract of <em>P. oedogonium</em> inhibited the growth of two bacterial and two fungal species viz: <em>Salmonella 1</em> (egg), <em>Staphylococcus</em> sp., 4978, <em>F. solini</em> and <em>P. viridicatum</em>. The maximum activity was observed against <em>F. solini</em> (22.3 mm) at 2 mg/mL conc. applied. It was noted that the growth of <em>Salmonella 1</em> (egg) was inhibited maximally at 4 mg/m Lshowing zone of inhibition of 7, 4.67 and 4 mm at 6 and 8 mg/mL conc., respectively. The inhibitory zones of 7 and 3 mm were recorded for <em>Staphylococcus</em> sp., 4978 at 4 and 8 mg/mL conc. used. Among fungal species <em>P. viridicatum</em> showed maximum Zone of Inhibition (ZOI) of 7.6 mm at 8 mg/mL conc. The ethanolic extract of <em>P. oedogonium</em> can be efficiently used in antibiotics production as it proved effective against <em>Salmonella 1</em> (egg), <em>Staphylococcus</em> sp., 4978, <em>P. viridicatum</em> and <em>F. solini</em>.

Chemistry, Antioxidant and Antimicrobial Potentials of White Pepper (Piper nigrum L.) Essential Oil and Oleoresins

The antioxidant and antimicrobial potentials of volatile oil and oleoresins of white pepper (Piper nigrum L.) was investigated in the present study. The white pepper essential oil has shown strong activity for the inhibition of primary and secondary oxidation products in mustard oil added at 0.02 % concentration which was evaluated using peroxide value and thiobarbituric acid value. Moreover it was further supported by complementary antioxidant assays such as ferric thiocyanate method in linoleic acid system, chelating and scavenging effects on 1,1′-diphenyl-2-picrylhydrazyl radical. In antimicrobial investigations, using inverted petriplate and food poison techniques, white pepper essential oil showed strong inhibition for Fusarium graminearum and Penicillium viridicatum. The white pepper ethanol and n-hexane oleoresin showed moderate inhibition for all tested fungal strains. Gas chromatography–Mass spectrometry (GC–MS) technique was used to analyze 40 different components constituting approximately 97.7 % of the volatile oil. Among them β-caryophyllene (16.0 %), sabinene (12.6 %), limonene (11.9 %) and torreyol (9.3 %) were the major components with many minor components. Both ethanol and n-hexane oleoresins comprise of 26 components having piperine, as the major component.

Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae at 23–30 °C

Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a(w)) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80-0.94 a(w)) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae. Among the applied storage parameters, a(w) turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a(w), which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a(w), fungal activation occurred within 24-48 h. The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a(w) and temperature of grain, which are easy to measure in practice.

Degradation of purine ribonucleosides by extracts of Penicillium viridicatum

Cell-free extracts of nitrate-grown Penicillium viridicatum could catalyze the hydrolytic cleavage of N-glycosidic bond of adenosine, guanosine and inosine to the corresponding base and ribose by a ribonucleoside hydrolase; however, there is no evidence for the degradation of these compounds through phosphorylation. The rate of hydrolysis of the three ribonucleosides was in the order inosine> guanosine> adenosine. It was proven that adenosine hydrolyzing enzyme is not associated with the cell membrane. Maximum enzyme activity was observed at pH 4 and 50°C. Heat inactivation kinetics and the effect of the nature of the buffer on enzyme activity revealed that, the cleavage of the three purine ribonucleosides is affected by one intracellular nucleoside hydrolase. It was proven experimentally that, all the metal ions tested had a remarkable inhibitory effect on the activity of the ribonucleoside hydrolase. Results obtained indicate that extracts of P. viridicatum catalyzed the conversion of guanosine into guanine and ribose by a nucleoside hydrolase and the resulting guanine was then deaminated to xanthine by an inducible guanine deaminase. In addition, xanthosine was not split into ribose and xanthine by the same extracts under the same experimental conditions and even at different pH values of the reaction mixture. Key words: Purine ribonucleosides, adenosine, guanosine, inosine, hydrolase, Penicillium viridicatum.

Production of Pectate Lyase by Penicillium viridicatum RFC3 in Solid-State and Submerged Fermentation.

Pectate lyase (PL) was produced by the filamentous fungus Penicillium viridicatum RFC3 in solid-state cultures of a mixture of orange bagasse and wheat bran (1 : 1 w/w), or orange bagasse, wheat bran and sugarcane bagasse (1 : 1 : 0.5 w/w), and in a submerged liquid culture with orange bagasse and wheat bran (3%) as the carbon source. PL production was highest (1,500 U mL−1 or 300 Ug−1 of substrate) in solid-state fermentation (SSF) on wheat bran and orange bagasse at 96 hours. PL production in submerged fermentation (SmF) was influenced by the initial pH of the medium. With the initial pH adjusted to 4.5, 5.0, and 5.5, the peak activity was observed after 72, 48, and 24 hours of fermentation, respectively, when the pH of the medium reached the value 5.0. PL from SSF and SmF were loaded on Sephadex-G75 columns and six activity peaks were obtained from crude enzyme from SSF and designated PL I, II, III, IV, V, and VI, while five peaks were obtained from crude enzyme from SmF and labeled PL I′, II′, III′, IV′, and VII′. Crude enzyme and fraction III from each fermentative process were tested further. The optimum pH for crude PL from either process was 5.5, while that for PL III was 8.0. The maximum activity of enzymes from SSF was observed at 35°C, but crude enzyme was more thermotolerant than PL III, maintaining its maximum activity up to 45°C. Crude enzyme from SmF and PL III′ showed thermophilic profiles of activity, with maximum activity at 60 and 55°C, respectively. In the absence of substrate, the crude enzyme from SSF was stable over the pH range 3.0–10.0 and PL III was most stable in the pH range 4.0–7.0. Crude enzyme from SmF retained 70%–80% of its maximum activity in the acid-neutral pH range (4.0–7.0), but PIII showed high stability at alkaline pH (7.5–9.5). PL from SSF was more thermolabile than that from SmF. The latter maintained 60% of its initial activity after 1 h at 55°C. The differing behavior of the enzymes with respect to pH and temperature suggests that they are different isozymes.